While clinicians recognize that fetal swallowing of amniotic fluid illustrates continuing intestinal activity throughout most of pregnancy., in sick very low birth weight neonates (weighing less than 1500g at birth), enteral nutrients are typically withheld after birth for extended periods of time. The attendant intraluminal starvation may inadvertently contribute to the occurrence of sepsis and necrotizing enterocolitis by causing aberrant gut colonization and increasing the potential for bacterial translocation across the intestinal epithelium. Current thinking suggests that providing dilute enteral substrate incremented over the first weeks of life will allow the earlier adaptation of enteral function, improve its barrier capacity, and result in a concurrent reduction in the complications associated with the use of total parenteral nutrition. To this end we seek to extend our previous experience with gut priming (beginning enteral fluids on 3rd postnatal day) by comparing the tolerance to and protein synthesis resulting from a commercially available predigested protein hydrolysate formula (Pregestimal) versus an intact protein based commercial preparation (Premie24). We will determine: 1) whether nutritional tolerance, growth, and mineral status can be augmented by the early by the early provision of incrementally adjusted enteral nutrients (gut-priming) over the first four weeks of life by comparing two commercially available formula preparations to fortified human breast milk. 2) Whether body protein synthesis and degradation are altered when providing nutrient as a predigested protein formula compared to either an intact protein product or breast milk at 3 days, 2 and 4 weeks postnatal age. 3) Whether tolerance of incremental increases in feeding is better when advancing volume of intake over concentration of the enteral fluid provided. 4) Whether the occurrence of problems such as necrotizing enterocolitis is affected by these interventions. 5) Whether serum IgG levels differ in patients where proteolysis is induced by exposure to intact formula protein compared to predigested protein versus breast milk.